The goal of this proposal is to identify the genetic basis for polycythemia vera (PV), essential thrombocythemia (ET) and agnogenic myeloid metaplasia (AMM), and to develop more effective treatments or these disorders based on genetic insights into disease pathogenesis. We hypothesize that PV, ET and AMM are due to activating mutations in tyrosine kinases. The hypothesis is based on the observation that the majority of myeloproliferative disorders (MPDs) characterized thus far are caused by activating mutations n tyrosine kinases, including chronic myelogenous leukemia, hypereosinophilic syndrome, and chronic myelomonocytic leukemia. Despite these examples of advances in our understanding of molecular pathogenesis of MPD, the genetic cause of PV, ET or AMM is completely unknown, due in part to rarity of the diseases, lack of heritability, and lack of cytogenetic clues to the identity of the mutant kinases. The Specific Aims of this proposal are to characterize the role of tyrosine kinase activation in the pathogenesis of PV, ET and AMM. We will use state-of-the-art genome wide screens to discover novel tyrosine kinase mutations, characterize the functional consequences of mutations, and develop specific inhibitors to mutant kinases as potential therapeutic agents. Because these diseases are relatively rare, a key to success of the proposal is acquisition of blood and buccal mucosal swabs from a large cohort of patients which has been successfully achieved. As an exciting proof-of-principle for this approach, we have recently identified JAK2V617Fmutations in most patients with PV and in some patients with ET/AMM. The Specific Aims are: 1. To use DNA sequence analysis to identify mutations in conserved domains of tyrosine kinases. 2. To use a custom designed oligonucleotide CGH array to discover intersitial deletions that activate tyrosine kinases. 3. Functional characterization of JAK2V617F and other novel genomic events leading to tyrosine kinase activation using in vitro and in vivo assays. 4. Develop and test kinase inhibitors against JAK2V617F and other activated tyrosine kinase using in vitro and in vivo assays. Although beyond the scope of this K08 proposal, the long term goal of this research is to expand the paradigm of tyrosine kinase inhibition as safe and effective therapy for cancer to include the myeloproliferative diseases PV, ET and AMM. We plan to develop preclinical data that will provide a platform for initiating clinical trials with novel kinase inhibitors. (End 0f Abstract)